The present invention relates to a static pressure sliding block, particularly to a static pressure sliding block supported movably using a pressure transmission medium.
A processing machine is known in the prior art to cut, grind and otherwise an optical device and molding die (Patent Document 1). Such a machine is provided with a static pressure sliding block to ensure high-precision traveling of the workbench.
[Patent Document 1] Tokkai No. 2003-39294
To more precisely generate the complicated curved surface corresponding to the aspherical surface of an optical device, it is important to meet the following requirements more sufficiently than the prior art machine.
[Requirements for Higher Precision]
(1) To improve the control precision of a machine, it is important to improve the resolution for position measurement of each axis, and to provide high-precision control of a workbench (slide table or turn table) driven by a high-speed servo mechanism. Further, to ensure quick response to the drive command of the servomotor, it is important to use a low-density material to reduce the weight of the static pressure sliding block being driven. (2) Since each axis is designed in a two- or three-stage building block structure, structural rigidity tends to be reduced. To avoid this, it is necessary to increase the rigidity of each axis and to raise the supporting rigidity of the pressure transmission medium for this purpose. Further, it is important to use material having a higher Young's modulus. (3) It is very important to provide resistance to changes in ambient temperature. When a static pressure sliding block is utilized, it is important to improve the supporting rigidity of the pressure transmission medium and to ensure that each member is made of material having a small linear expansion coefficient to avoid useless heat generation. (4) It is important to ensure that processing is terminated before a large ambient change occurs, and to reduce the machining time in order to achieve highly efficient machining. To achieve high-speed driving of the axis, it is important to increase the speed of the servomechanism so as to conform to high resolution for position measurement. In order to avoid deterioration of the rigidity in the static pressure receiving surface or to prevent vibration, it is important to improve the supporting rigidity of the pressure transmission medium.
To reduce the weight of the static pressure sliding block, ceramic can be employed instead of metal used as a material. In the meantime, to enhance supporting rigidity of the pressure transmission medium, oil can be used instead of a gas. However, if the static pressure sliding block is made of metal, a tapped hole can be formed in the static pressure receiving surface by tapping operation, and an orifice member for adequate discharge of the pressure transmission medium can be screwed directly into the tapped hole. By contrast, when the static pressure sliding block is made of ceramic, it is difficult to form a tapped hole, and may be damaged because of its brittleness when the orifice member is screwed into the hole even if the hole could be tapped. To solve this problem, an adhesive is used to secure the orifice member on the ceramic static pressure sliding block. However, when oil is used as a pressure transmission medium, the adhesive may dissolve or be denatured, and adhesive force may be deteriorated, resulting in the orifice member being disengaged.